Electronic mail, commonly referred to as email, is a method of exchanging digital messages across the Internet or other computer networks. Historically, email was transmitted directly from one user's computer to another user's computer, which required both computers to be online at the same time. Today's email systems are based on a store-and-forward model. Email servers accept, forward, deliver, and store messages. Users are no longer required to be online simultaneously and need only connect briefly, typically to an email server, to send or receive messages.
An email client, also referred to as email reader or mail user agent, is a computer program used to manage a user's email. In addition, web-based email applications allow a user to manage emails using a web browser.
Businesses receive large quantities of emails, and it can be difficult for a recipient of the emails to determine at a first glance which emails need to be read and acted on first, and which emails can wait. The recipient often fails to realize that important email is waiting in the inbox to be processed. As a result, important business opportunities may be lost, and important customers may not be given the best service.